Birth or baptism/death or burial?
In the United Kingdom, civil registration of births, deaths and marriages began on 1 July 1837. Prior to this date, baptisms, marriages and burials were recorded by individual parish churches. You may find the occasional reference to a birth or death date in parish records but this is the exception rather than the rule.
Why is the date Q1 1840?
The GRO index groups records by quarters: Jan-Mar (Q1), Apr-Jun (Q2), Jul-Sep (Q3) and Oct-Dec (Q4). An important consideration is that events were not necessarily recorded in the quarter they occurred.
Why is the date 1700/01?
The Gregorian calendar was introduced during the tenure of Pope Gregory XIII in October 1582 but it was not universally adopted at this time. The Calendar (New Style) Act 1750 received royal assent in Great Britain on 27 May 1751 and was adopted in England on 1 January 1752. Prior to 1752 the calendar year began with the Feast of the Annunciation which was held on 25 March.
The main concern for family historians is the year of a parish entry. You may stumble across a baptism for an ancestor transcribed as 3 February 1740. This would refer to the calendar year of 25 March 1740 – 24 March 1741. Using our modern viewpoint (with the year commencing on 1 January) this baptism would be recorded as 3 February 1741. So, for clarification purposes, the date is recorded as 3 Feb 1740/41.
Being resistant to change is timeless. While the Gregorian calendar (and the 1 January) was officially adopted in 1752 in Great Britain, you may stumble across parish entries using the Julian calendar after this date. Be cautious when viewing transcripts of this period as the year of entry may differ depending on who transcribed the entry. Make a note that the source is a transcription and not the original document.